Download or read book Determining the Potential Drop Calibration of a Fatigue Crack Growth Specimen Subject to Limited Experimental Observations written by PC. McKeighan and published by . This book was released on 1994 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Six separate calibration techniques are applied to potential drop (PD) and crack length data from 23 experimental datasets. Five of the techniques use limited experimental input gained during precracking and after test completion to derive the coefficients associated with the calibrations. The datasets include SE(B) and M(T) specimens, fatigue crack growth (FCG) tests and foil analog simulations as well as various aluminum alloys and steel. A comparison of the calibration techniques is undertaken in terms of crack length and the subsequent effect on stress intensity factor errors. The best calibration techniques using two PD and crack length data pairs are the two-point modified and post-test corrected Johnson's equation. Using these methods, 21 of the 23 tests satisfy a criterion based on an acceptable ±2% mean variation in stress intensity factor. If a statistical assessment of the data is made, only 30 to 35% of the tests satisfy this criterion. Finally, the crack length prediction errors that result from the different calibrations can typically cause a 15 to 30% variation in FCG rate da/dN at a given ?K level. This difference is found to be primarily due to errors in the ?K calculation.
Download or read book Fatigue Testing and Analysis Under Variable Amplitude Loading Conditions written by Peter C. McKeighan and published by ASTM International. This book was released on 2005 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nontraditional Methods of Sensing Stress Strain and Damage in Materials and Structures written by Peter C. McKeighan and published by ASTM International. This book was released on 2001 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: A further 13 papers from a November 1999 symposium in Kansas City, Missouri cover fracture mechanics and structural integrity, damage evolution and measurement, and techniques to measure strain and displacement. The topics include sensing crack nucleation and growth in hard alpha defects embedded in
Download or read book Development of a Fatigue Crack Growth Rate Specimen Suitable for a Multiple Specimen Test Configeration written by FR. Deshayes and published by . This book was released on 1993 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new experimental approach developed by fatigue crack growth rates can be determined for multiple specimens tested in series. This involves a geometry such that the response to cyclic loading in each specimen is mutually independent. Relationships between the stress intensity factor, compliance, and crack length and between direct-current potential drop and crack length have been analytically evaluated for the proposed specimen geometry. An appropriate side-groove depth that avoided crack deviation from the intended plane of extension was determined experimentally, and an analytical expression that accounted for reduced thickness in the crack plane was verified. Calibration curves between crack length and compliance and between crack length and potential drop were experimentally verified as well, and the stress intensity-crack length characteristics for the specimen were confirmed by comparing da/dN-?KI curves with those for conventional C(T) specimens. A customized, five specimen frame was designed and fabricated in conjunction with a 98-kN MTS actuator and interfaced with a commercially available control system, the hardware and software of which were modified to accommodate multiple-specimen control and data acquisition. The utility of the proposed specimen and test procedure is discussed within the context of threshold and near-threshold crack growth rate determinations where long test times are normally required for data development, particularly for low cyclic frequency applications such as nuclear and offshore.
Download or read book Fatigue and Fracture Mechanics written by Richard Edward Link and published by . This book was released on 2007 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book On the Experimental Calibration of a Potential Drop System for Crack Length Measurements in a Compact Tension Specimen written by G. Belloni and published by . This book was released on 2002 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present study was focused on the setup of a system for monitoring deep cracks in notched specimens in creep and fatigue laboratory tests. The test configuration features, the instrumentation requirements, and the important problems of the calibration for potential drop application to both fatigue and creep crack growth tests on compact tension specimens are discussed in detail. Experimental tests on the compact tension specimen geometry were carried out at ambient and high temperatures in order to define and validate an experimental calibration for this specimen geometry, to check the effect of temperature, and to compare the crack growth calibration curves under creep or fatigue conditions.
Download or read book Metals Abstracts Index written by and published by . This book was released on 1996 with total page 1622 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Potential Drop Method for Measuring Fatigue Crack Growth written by A. E. CARDEN and published by . This book was released on 1973 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt: IN FATIGUE CRACK GROWTH (FCG) EXPERIMENTS TWO OF THE ESSENTIAL MEASUREMENTS ARE CRACK LENGTH AND CYCLE NUMBER. CRACK LENGTH MEASUREMENT GENERALLY HAS THE LEAST PRECISION AND IS THE MOST EXPENSIVE TO OBTAIN SINCE IT IS USUALLY VISUALLY OBSERVED AND MANUALLY RECORDED. SEVERAL ATTEMPTS HAVE BEEN MADE TO AUTOMATE THE MEASUREMENT AND RECORDING OF THE CRACK LENGTH BUT THE PRECISION WAS LOW WHEN THE CRACK LENGTHS ARE SMALL. A POTENTIAL DROP METHOD DEVELOPED BY MARKOCHEV HAS BEEN APPLIED TO FCG AT ELEVATED TEMPERATURE ON CN SHEET AND CT 2T SPECIMENS WITH GOOD RESULTS. A DIVIDER CIRCUIT GIVES THE RATIO OF THE POTENTIAL DROP NEAR THE CRACK TIP TO THAT IN A SHUNT. OUTPUT IS THEREFORE INSENSITIVE TO CURRENT LEVEL. THE DERIVATIVE OF THE OUTPUT VERSUS CRACK LENGTH IS CONSTANT FROM THE INITIAL CRACK LENGTH TO ABOUT 1/2 A/W. WITH OPERATIONAL AMPLIFIERS AND A MILLIVOLT RECORDER, CRACK LENGTH VERSUS CYCLE NUMBER CAN BE CONTINUOUSLY RECORDED. THE THRESHOLD LEVEL FOR FCG CAN BE MUCH MORE PRECISELY DETERMINED. INCUBATION PERIODS FOR FCG ARE CLEARLY OBSERVED AFTER OVERLOADS. FCG OF 10 TO THE 8TH POWER IN/CYCLE ARE EASILY DEFINED. THE THRESHOLD DELTA K FOR INCOLOY WAS DETERMINED TO BE ABOUT 4 KSI(IN) 1/2 IN LESS THAN 60 HOURS OF TESTING. WITH VISUAL OBSERVATION THE THRESHOLD LEVEL WAS JUDGED TO BE ABOUT 8 KSI(IN) 1/2 IN ABOUT 300 HR OF TEST TIME. THE LOWEST CRACK GROWTH RATE IN THE VISUAL METHOD WAS ABOUT 10 TO THE MINUS 7 IN/CYCLE.
Download or read book Applied Science Technology Index written by and published by . This book was released on 1995 with total page 1804 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Determination of Fatigue Crack Growth Rate by the Potential Drop Method Set up and Calibration written by O. Vosikovsky and published by . This book was released on 1975 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1996 with total page 970 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Determination of Calibration Function for Fatigue Crack Propagation by Measurement Surface Deformation written by J. Predan and published by . This book was released on 2015 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: Components and structures exposed to elastic dynamic loading respond with elastic strains on the surface of the material. Mechanical response could be monitored by deformations on the surface. The measurements and monitoring of these parameters could be performed with electronic devices for on-line measurements, controlled by computerized systems. Fatigue-induced flaw growth was monitored on a four-point specimen, loaded by cyclic dynamic bend forces. The flaw growth was monitored by strain gauges with a standard resistance of 120 ?. After performance of fractal-graphical measurements, a flaw-growth analysis was performed to determine the shape, propagation, and cross sections of the crack. To determine the stress-intensity factor, a numerical model was developed based on measured crack shapes, material properties, and cyclic loading data of the actual tested specimen. The investigation results showed that the derived calibration curve could be used to predict surface deformations as a result of crack propagation and growth, but not crack initiation. With the determination of surface deformation, one could follow the crack transition from the semi-elliptical surface crack to the through-thickness crack. The stress-intensity factor has been determined numerically by using the finite-element method for five different fatigue-crack fronts. Results show that fatigue crack on the surface of specimens propagated under an almost constant stress-intensity factor value. Consequently, in our case, the fatigue-crack growth rate was constant during transition from a surface semi-elliptical crack to a through-thickness crack front. The aim of this paper is to describe methodology and results based on experimental and numerical modeling during crack propagation and potential use of this technique for online monitoring purposes.
Download or read book Investigation of Constraint Effect on Fatigue Crack Growth Rate Measurements written by Veronika Hochfellner and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: For the purpose of reliable life prediction the fatigue crack growth behaviour of a material has to be well-known. Therefore standardized fatigue crack growth tests are made with test specimens of the material. The obtained fatigue crack growth data is taken as material specific data and is given without any information of the test conditions and used specimen geometry. However, in several studies a geometry dependency of the test specimen on the fatigue crack growth data is found. Hence in this investigation experiments on fatigue crack growth behaviour are made with two different specimen geometries, the middle tension specimen M(T) and the compact (tension) specimen C(T). The direct current potential drop (DCPD) method is used to determine the crack lengths which is calibrated with the aid of beach marks and crack detection gauges. Two different configurations of the DCPD method are implemented to gain acceptable results. With the obtained data fatigue crack growth curves are established which are analysed regarding the geometry influence of the used test specimens. Discrepancies in the fatigue crack growth curves between the tested specimens are found. With these findings an approach is tested to create a material curve which is independent of the specimen geometry. However, this approach is not leading to satisfactory results. The implementation of the DCPD method in its main configuration on the used experimental setup proves to be applicable for fatigue crack growth tests on different geometries and will be used in further studies at low temperatures.
Download or read book Fatigue Crack Growth Measurement and Data Analysis written by S. J Hudak and published by ASTM International. This book was released on 1981 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metals Abstracts written by and published by . This book was released on 1996 with total page 1650 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Determination of Stress Intensity in a Cracked Cylindrical Specimen written by Graham Clark and published by . This book was released on 1980 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The range of stress intensity at the tip of a fatigue crack is the major factor controlling the crack growth rate, and the relationship between these two parameters for any one material is easily established from crack growth rate measurements in a specimen geometry for which the stress intensity calibration is known. However, in a different specimen geometry made from the same material, different crack growth rates will be observed, and it is possible to use this relationship to determine the stress intensity calibration for the second geometry from a comparison of crack growth rates in the two specimens. This report describes such a stress intensity calibration procedure for a hollow cylindrical specimen containing a crack which grows radially from the bore under the influence of compressive loading across a diameter of the ring. The stress intensity determined experimentally is shown to be in close agreement with the results of a theoretical study. (Author).
Download or read book A High Sensitivity Potential Drop Technique for Fatigue Crack Growth Measurements written by Graham Clark and published by . This book was released on 1979 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes the design features of a highly sensitive and accurate system for monitoring the growth of fatigue cracks in laboratory specimens of various geometries. The system is based on the potential-drop method which utilizes the electrical resistance changes associated with fatigue crack growth through the specimen cross-section to detect crack length increments of a few micrometers. The technique is suitable for automation, and tests may be completed with a minimum amount of operator interference. A computer-based data-processing method is described, and the performance of the system in measuring both absolute crack length and crack growth rate is evaluated.
